The present invention relates to an escalator system having pulse-free turnarounds and transition zones and a method for designing the escalator system.
The step assembly of an escalator forms a chain of rigid links. The links are supported by rollers which move around a smooth closed track. At the top and bottom of the escalator, the tracks xe2x80x9cturn aroundxe2x80x9d, reversing the direction of travel. Typically, the velocity of the step entering the turnaround differs from the velocity of the step having exited the turnaround. This is experienced as a cyclical velocity pulsation at the link passage frequency. As part of this experience, the rollers may periodically lift off the track or the joints and rollers may be subject to excessive loads alternately binding and stretching. This xe2x80x9cpolygon-effectxe2x80x9d vibration can result in unacceptable ride quality. The same effect can occur to a lesser degree in the transition regions between the escalator rise and the upper and lower landings.
Polygon-effect vibration is typically addressed by defining roller paths with sufficiently large radii for turnarounds and transitions. Haruta et al., in the article xe2x80x9cA Super High-Rise Escalator With a Horizontal Mid-Sectionxe2x80x9d, Elevator Technology 6, Proceedings of ELEVCON ""95, March 1995, pp. 78-87, describe a design method for choosing optimal constant radii for minimization of the polygon effect. Despite the existence of this design method, there remains a need for a design method and an escalator which has a truly pulse-free turnaround.
Accordingly, it is an object of the present invention to provide an escalator system which has pulse-free turnarounds.
It is another object of the present invention to provide an escalator system as above having pulse-free transition zones.
It is a further object of the present invention to provide a method for designing an escalator system having pulse-free turnarounds and/or pulse-free transition zones.
The foregoing objects are attained by the escalator system and the design method of the present invention.
In accordance with the present invention, an escalator system is provided which broadly comprises a pair of guide tracks, and a pair of linkage assemblies each comprising a plurality of links joined together. Each linkage assembly has a plurality of rollers for supporting the linkage assembly, which rollers travel in a respective one of the guide tracks. Each guide track has two spaced apart turnaround portions with each turnaround portion defining a travel path for each roller having a linear entry section, a linear exit section, and a curved pulse-free section. The escalator system may further have at least one pulse-free transition zone.
Further, in accordance with the present invention, a method for designing an escalator system broadly comprises designing each turnaround to be pulse-free by selecting a trajectory to connect two linear sections, determining a number of links which fit the selected trajectory, determining an initial configuration for the links where a first joint associated with a first one of the links travels in a linear direction and a second joint associated with a last one of the links travels in a linear direction; and determining a trajectory of a third joint located between the first and second joints as the third joint passes through the turnaround section. The method further comprises designing at least one pulse-free transition zone.
Other details of the pulse free escalator system and design method of the present invention, as well as other objects and advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings, wherein like reference numerals depict like elements.